This invention concerns beneficiation of superconducting material in powdered form by separating particles thereof which are more superconducting from those that are non-superconducting or contain substantial non-superconducting phases.
It has long been known that certain materials conduct electricity at very little loss at temperatures near absolute zero. Nearly half of the elements on the periodic chart, and a very wide range of compounds and alloys, exhibit some decrease in electrical resistance when their temperatures are reduced to near absolute zero.
Recently, there have been substantial advances made in discovering new materials or compounds that are superconducting. Certain metal oxides - materials which in the past had been considered electrical insulators - have been found to have superconducting characteristics at transition temperatures (T.sub.c) well above absolute zero. This had led searches for still further compounds that will superconduct at even room temperature.
Present discoveries and developments lead the theory or understanding of just how recently discovered superconductors work. Understood or not, there is a common characteristic running through all superconducting materials. They levitate (float) in a sufficiently strong magnetic field. It was discovered that a superconducting metal, when cooled to below its critical temperature (T.sub.c), expelled a magnetic field. A magnet will levitate over a superconducting material below its critical temperature. Conversely, a superconducting material, when cooled to below its critical temperature (T.sub.c) will levitate in the magnetic field above either pole of a sufficiently strong magnet.
This effect, discovered in 1933 and known as the Meissner Effect, has been an interesting laboratory curiousity and found use in testing for superconductivity. Aspects of the principle are employed in the inventive process disclosed herein.
In a field unrelated to superconductivity, it is known to separate one metal from another by subjecting both to a magnetic field, wherein one is attracted by the field and other is not. This principle was employed as early as 1876 in U.S. Pat. No. 581,034 wherein gold-containing ore was passed through the presence of a magnetic field. More specifically, the process involved placing the ore above a bed of mercury, subjecting the ore to the influence of a magnetic field to draw the ore below the surface of the mercury, and removing the ore.
A process for separating relatively magnetic particles from relatively non-magnetic particles in a dry state is disclosed in more recent U.S. Pat. No. 4,478,711. In this process, particles flow past a magnet. The magnetic particles are diverted toward the magnetic, but are not retained by it, while non-magnetic particles continue along their original path. U.S. Pat. No. 4,565,624 discloses still another arrangement for separating magnetic ores from non-magnetic material. These processes are mentioned to illustrate examples in the art of using magnetic fields to separate magnetic ore from non-magnetic material such as soil or rock in which it is contained.
The present invention relates to a process for beneficiation of superconducting material in powdered form comprised of particles, grains, or granules having different superconducting characteristics. Particles, etc., which are more superconducting are harvested from other particles that are less superconducting or are non-superconducting. The invention employs a process for separating materials according to their relative superconductivity.